A semiconductor device of a so-called COF (Chip-On-Film) structure wherein a semiconductor element is joined to or mounted on a flexible wiring substrate has been used in a variety of fields, and hereinafter, the semiconductor device of the COF structure is referred to as a “COF-type semiconductor device”. Typical examples for applications of such COF-type semiconductor device include a liquid crystal driver adopting a semiconductor element of a liquid crystal driver integrated circuit (IC). The liquid crystal driver adopting the COF-type semiconductor device is structured such that one of the end portions of a flexible wiring substrate is connected to the liquid crystal display substrate for use in forming a liquid crystal panel, and the other end portion is connected to a printed wiring substrate, thereby forming a liquid crystal module.
The liquid crystal module adopting the COF-type semiconductor device can be formed in a thinner structure and is therefore suited for compact-size electronic equipments such as a portable telephone, a pager, a game machine, etc.
However, for the liquid crystal module adopting the COF-type semiconductor device, for example, as disclosed in Japanese Laid-Open Patent Publication No.11-249583/1999 (Tokukaihei 11-249583, published on Sep. 17, 1999), a structure wherein a flexible wiring substrate is folded down to the back surface side of a liquid crystal panel after connecting the flexible wiring substrate to the liquid crystal panel is known.
Specifically, as illustrated in FIG. 11, a display device as a liquid crystal module 100 of the above publication includes a semiconductor device 104 wherein a semiconductor element 103 is joined or mounted on a back surface of a flexible substrate 102 having formed thereon a wiring pattern 101.
One end portion of the flexible substrate 102 in the semiconductor device 104 is connected to a liquid crystal panel 108 composed of an upper glass substrate 106 and a lower glass substrate 107 interposed between polarization plates 105. Below the lower glass substrate 107, provided is a light-directing plate 110 supported by an upper frame 109. Further, along the side face of the light-directing plate 110, an LED (Light Emitting Diode) 111 is provided as a back light.
Below the upper frame 109, a lower frame 112 is provided, and between the upper frame 109 and the lower frame 112, a semiconductor element 103 mounted on the surface of the flexible substrate 102 is interposed so as to face downward. Namely, the semiconductor element 103 is stored in a recessed part of the lower frame 112, and the flexible substrate 102 is curved so as to have a cross section of substantially C-shape.
As described, the above display device has a connection part 113 formed on the upper glass substrate 106 of the liquid crystal panel 108, and the semiconductor element 103 is mounted on the flexible substrate 102 so as to be extended (projected) outward (downward in the FIG. 11).
In the foregoing liquid crystal module 100, if the connection part 113 is formed on the lower glass substrate 107, the semiconductor element 103 would be projected to the inside of the module main body. Conventionally, the above structure of forming the connection part 113 on the lower glass substrate 107 is adopted. In this conventional structure, however, the number of connection points for leading transparent wiring formed on the upper glass substrate 106 to the lower glass substrate 107 increases, and consequently, an area occupied by the connection points increases. For this reason, it is difficult to realize a compact size structure for an increased number of pixels. Therefore, in recent years, the structure wherein the connection part is formed on the upper glass substrate 106 is generally adopted for the reason that the number of connection points can be reduced by forming the transparent wiring of the lower glass substrate 107 in the upper part.
As illustrated in FIG. 12, in a conventional liquid crystal module 200 wherein a COF-type semiconductor device is connected to a liquid crystal panel in flat, an electrode 203 is formed on a lower glass substrate 202 of a liquid crystal panel 201. In this structure, in order to connect the semiconductor device 210 having a semiconductor element 214 mounted on the side of a conductor pattern 212 formed or the surface of a flexible substrate 211, it is required to turn over the semiconductor device 210 so that the semiconductor element 214 faces downward.
In this state, the semiconductor device 210 is connected to the liquid crystal panel 210 at one end portion of the flexible substrate 211, and the semiconductor device 210 is connected to the printed wiring substrate 214 at the other end portion of the flexible substrate 211.
As a result, a liquid crystal module 200 wherein the semiconductor device 210 is connected to the liquid crystal panel 201 in flat can be realized.
However, in the conventional semiconductor device and the liquid crystal module adopting the conventional semiconductor device have the following problems.
That is, in the liquid crystal module 100 illustrated in FIG. 11, the connection part 113 is formed on the upper glass substrate 106 of the liquid crystal panel 108. Therefore, in the structure of bending the flexible substrate 102, the semiconductor element 103 is inevitably projected to the outside. Consequently, a spacing for the thickness corresponding to the thickness of the semiconductor element 103 is required between the flexible substrate 102 and the main substrate 114, and a thinner structure is therefore difficult to achieved.
In the liquid crystal module 200 of the flat structure as illustrated in FIG. 12, the semiconductor element 214 is provided between the lower glass substrate 202 of the liquid crystal panel 201 and the printed wiring substrate 214 on the side of the semiconductor device 210, and therefore, a frame length L becomes longer.